wifi: mt76: mt7996: Add mcu commands for getting sta tx statistic

Per peer Tx/Rx statistic can only be obtained by querying WM when WED is
on. This patch switches to periodic event reporting in the case of WED
being enabled.

Signed-off-by: Yi-Chia Hsieh <yi-chia.hsieh@mediatek.com>
Signed-off-by: Money Wang <Money.Wang@mediatek.com>
Signed-off-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Signed-off-by: Evelyn Tsai <evelyn.tsai@mediatek.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>